White grubs proliferate in some lawns. Photo: www.the-scientist.com
If you’ve been dealing with white grubs in your lawn—and losing the battle more often than not!—there is a new biological control product you might want to consider: BTG (Bacillus thuringiensis galleriae). Yes, it has been sold to a limited degree for about 3 years now (and indeed, I’ve mentioned it in this blog in the past), but this year is seeing it on garden center shelves throughout North America. (Sorry, I’m not aware of its availability on other continents.)
How Do You Know If You Have White Grubs?
Usually, it’s pretty obvious!
They’re essentially a lawn pest. They may be present in other types of garden, but rarely do any visible damage. But they cause lawns to turn brown and even die.
Often, the first sign is when you notice holes dug in the lawn by mammals like skunks and raccoons, searching for the delicious grubs. Or hordes of birds like starlings and crows pecking at your turf.
Also, the lawn begins to turn yellow, then brown and will feel soft and spongy to walk on. If you take hold of a section of turf and try to lift it, it will come right off in your hands, its roots having been nibbled off by grubs.
When you pull the turf up, you may see them just underneath. If not, dig a bit deeper into the soil under the lawn and you’ll find them, smiling lazily at you.
What Are White Grubs?
White grubs are the larval stage of various scarab beetles, like June beetles, chafers and Japanese beetles. They’re plump C-shaped whitish creatures with tan or brown heads and 3 pairs of shot legs. They can be tiny at hatching time, but grow over time, some reaching up to 1 inch (2.5 cm) in length. They live under the lawn until late spring of the following year (3 years in the case of June beetle larvae) before going into a short pupal stage, then maturing into adult beetles.
The adults then dig their way out of the soil and feed on the foliage and flowers of nearby plants, often causing considerable damage (Japanese beetles and rose chafers, notably, are renowned for their destructiveness). Then, after a month or so, females return to lawns, especially low-mown ones, and lay the eggs of the next generation. They soon hatch … and the cycle begins anew.
What Is BTG?
Depending on where you live, you many find BTG (Bacillus thuringiensis galleriae) under various brand names. I’ve been seeing Grub B Gon Max locally, but you might find it under the names grubGONE!®, beetleGONE!®, BeetleJUS! or grubHALT!®, among others. (Don’t all those exclamation marks just drive you up the wall!!!)
BTG is a natural bacterium found in soils worldwide. It is specific to beetles in certain families: the Scarabaeidae, Buprestidae, Tenebrionidae and Curculionidae families, thus scarab beetles, wood-boring beetles (including emerald ash borers), darkling beetles and weevils. It will not harm other insects, such as pollinators (bees, butterflies, hoverflies) and predatory insects (wasps, lacewings, pirate bugs, etc.), nor even other beetles, like ladybugs. Nor is it harmful to humans, pets, mammals, birds, amphibians, fish or aquatic insects.
Some of the Lawn Pests Controlled by BTG
Asiatic garden beetle
June Beetle (May beetle)
Northern masked chafer
Southern masked chafer
Black turfgrass ataenius
Annual bluegrass weevil
Obviously, BTG is not harmful to lawn grasses of any species, nor indeed plants of any type.
The variety used is a selected strain called BTG SDS-502, easier to produce commercially and more effective against lawn pests than other strains.
When the larva consumes the bacterium, it produces crystal proteins that poison its host, causing it to stop feeding. The grub gradually becomes paralyzed, then dies. The results are often noticeable within a week or so, as turf often recuperates quite quickly once its roots are no longer being eaten.
The product is usually applied to lawns with a spreader (the same type used for applying fertilizer and lawn seed), then watered in so the bacteria descend into the soil layer where the larvae live. Powdered forms can also be sprayed onto the foliage of susceptible plants to control adult insects, but they do not appear to be widely available at this time.
BTG can be applied to lawns at any time from spring through late fall. Usually, though, the best results are obtained by applications in July or August, timed to reach young larvae just emerging from eggs laid by adult females (they hatch in 10 to 30 days, depending on the species). However, many gardeners apply it in spring to control the damage animals cause as they search for larvae, in which case a second treatment will likely be needed in summer or fall to reach the grubs of the next generation.
Not to Be Confused With…
BTG is not the same thing as another grub treatment, beneficial nematodes. In fact, the two actually complement each other, each attacking grubs in different ways. Nor is it the same thing as milky spore disease (Paenibacillus popilliae), used specifically to control Japanese beetle larvae.
Is BTG Effective?
You tell me! I’m generally hearing very positive feedback about this product, but it’s fairly new. Time will probably tell. And I won’t be able to test it myself, as I’ve never had a white grub problem.
Certainly, it would be worth trying if white grubs are ruining your lawn, especially if you’ve been using poisonous chemicals to control them or hiring lawn care companies to do the dirty work for you. And if enough neighbors use it, it might also bring down the damages from adult beetles, like Japanese beetles, to a more acceptable level.
Try it and see!